MadSci Network: Physics
Query:

Re: How can you demonstrate a homemade lightbulb? See comments...

Date: Tue Mar 30 11:16:23 1999
Posted By: William Beaty, Electrical Engineer / Physics explainer / K-6 science textbook content provider
Area of science: Physics
ID: 918063711.Ph
Message:

I've seen a similar demonstration which used thin Nichrome alloy wire (the same stuff that's used in toasters and electric heaters.) Alligator clip-leads are used to connect a piece of Nichrome wire to a heavy-duty battery, such as a 6-volt lantern battery. If the wire glows too brightly and burns through too fast, either use a longer piece of wire (more ohms), or replace your 6V battery with two or three D-cells hooked in series (less volts).

You might even experiment with removing the oxygen from around the wire to make the "light bulb" last a bit longer. A big jar full of C02 (from a small chunk of dry ice, or from vinegar/baking-soda) might make the glowing filament last longer. Or if you have liquid nitrogen available, put a small paper cup full of LN2 in your big jar, and the cloud of nitrogen gas will push the air out. (Conventional light-bulbs don't contain a vacuum, they actually use low-pressure argon and nitrogen gases.) Comparing a bare filament with a filament immersed in a non-oxygen environment might be a worthwhile demonstration too.

If you go hunting for Nichrome wire, try to find some that's very thin, like 28-gauge or so. Try the various science mail-order supply companies (there are several linked through my suppliers page.

Another source of very thin and inexpensive wire: steel wool! If you unroll a batt of steel wool (the grey kind, not the copper-colored pads), you can tease out many thin fibers. If you use extra fine 0000-grade steel wool, you can probably make it glow with just a single 1.5v D-cell.

See also: Why does a 9V battery ignite steel wool?


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